function AT_ekf(v){
	function ekf(o,s1,s2){
		var i,N,t=[0],t2=[],ot={},os={};
		var v1=1/s1,v2=1/s2;
		var s=Math.round(2/(v1+v2)),a=(v2-v1)/(s-1);
		t2[s]=1
		for(i=1;i<=s;i++){
			t[i]=t[i-1]+v1;t2[s-i]=t2[s-i+1]-v2
			v1+=a;v2-=a
		}
		for(i in o)os[i]=v.van.a[i]
		for(i=1;i<=s;i++){
			for(p in o)ot[p]=(v.van.a[p]!=N)?os[p]+(o[p]-os[p])*(((s-i)*t[i]+i*t2[i])/s):o[p]
			v.van.KF(ot,1)
		}
		return s
	}
	return ekf
}